Proeryon giganteus Beurlen, 1930

Audo, Denis & Schweigert, Günter, 2018, Large polychelidan lobsters with a rounded carapace from the Middle Jurassic La Voulte-sur-Rhône Lagerstätte: taxonomic clarifications, Geodiversitas 40 (9), pp. 183-194 : 192

Proeryon giganteus Beurlen, 1930

Proeryon giganteus Beurlen, 1930: 219-222 , fig. 1, pl. 15. — Kuhn 1952: 156, fig. 1. — Garassino & Gironi 2006: 59.

Proeryon laticaudatus – Schweitzer et al. 2010: 44.

Proeryon zehentbaueri – Audo et al. 2014c: 508.

TYPE MATERIAL. — Holotype by monotypy in the collections of Urwelt-Museum Hauff (Holzmaden, Germany), without collection number.

TYPE LOCALITY. — Holzmaden, Baden-Württemberg, Germany.

TYPE AGE. — Early Toarcian, Falciferum ammonite Zone.

DISCUSSION

Schweitzer et al. (2010) considered Proeryon giganteus Beurlen, 1930 as a junior synonym of P. laticaudatus Beurlen, 1928 . Audo et al. (2014c) disagreed with this synonymy and considered P. giganteus and P. laticaudatus to be separate species. As these authors assigned Eryon giganteus to Proeryon – based upon the paratypes herein excluded from type material, Proeryon giganteus Beurlen, 1930 was considered a secondary homonym of P. giganteus Van Straelen, 1923 . The rediscovery of the lectotype of E. giganteus and the resulting new assignment of E. giganteus to Soleryon is that this species is no longer homonymous with P. giganteus Beurlen, 1930 . Therefore, the replacement name Proeryon zehentbaueri , for Proeryon giganteus Beurlen, 1930 is abandoned ( ICZN 1999: article 59.4).

CONCLUSION

The rediscovery of the lectotype of Eryon giganteus had a domino effect on the complicated and unstable taxonomy of the “large polychelidans with a rounded carapace” from La Voulte-sur-Rhône. Audo et al. (2014c) had already remarked that two species were mingled in the descriptions of these polychelidans, leading to a succession of conflicting generic assignments. Yet, Audo et al. (2014c) did not notice that the name E. giganteus , as defined by its lectotype, is not attached to the most iconic and abundant species of polychelidan in La Voulte, but rather to a rarer species probably belonging to the genus Soleryon .

The present case clearly stresses the possible consequences of the rediscovery of type material, and in this respect, is reminiscent of the rediscovery of the type material of Eryon cuvieri (see Charbonnier et al. 2012).

This rediscovery of the lectotype of E. giganteus will undoubtedly cause some confusion for the specialists and enthusiasts who have been or will be working on the fossil crustaceans from La Voulte. Indeed, the most abundant species was usually referred to as “ Eryon giganteus ” “ Coleia gigantea ” or “ Proeryon giganteus ”. Now, the species giganteus is relegated to being a rather rare species (six specimens known to date, compared to 33 specimens of P. charbonnieri n. sp.). While such a change does not justify a decision of the International Commission on Zoological Nomenclature (ICZN), it still complicates understanding species discussed by previouslypublished researches, especially so as these two species from La Voulte had been confused for decades. The case of Proeryon giganteus Beurlen, 1930 is also confusing, albeit far less, as it was briefly known for another name for a few years.